Tuesday, December 30, 2014

When there is a job stuck and cannot be remove by a normal qdel, you can use the command qdel -p jobid. Do note that this command should be used when there is no other way to kill off the job in the usual fashion especially if the compute node is unresponsive.

If you encountered the "cannot change directory to /home/user1. Permission denied on NFS mount" when you do a su --login user1. Do check the base directory permission. If the owner and group /home is root.root, do remember to chmod 755

Friday, December 19, 2014

Symptom:
The symptom can range from random disconnection to slowness in the entire school/building wired network. Eventually, the cause of this problem was found to be due to intel-chipset nic card (Intel I2xx/825xx series) sending out erratic & massive multicast traffic, causing flooding of the network and high CPU on the switches. The below link are some url which describe the same problem faced by other user environment:

Resolution:
The recommended step to resolve this problem is to upgrade the intel nic card driver to version 19.0 and above.

Tuesday, December 9, 2014

Storage Systems
SuperMUC has a powerful I/O-Subsystem which helps to process large amounts of data generated by simulations.

Home file systems
Permanent storage for data and programs is provided by a 16-node NAS cluster from Netapp. This primary cluster has a capacity of 2 Petabytes and has demonstrated an aggregated throughput of more than 10 GB/s using NFSv3. Netapp's Ontap 8 "Cluster-mode" provides a single namespace for several hundred project volumes on the system. Users can access multiple snapshots of data in their home directories.

Data is regularly replicated to a separate 4-node Netapp cluster with another 2 PB of storage for recovery purposes. Replication uses Snapmirror-technology and runs with up to 2 GB/s in this setup.

Work and Scratch areas
For highest-performance checkpoint I/O IBM's General Parallel File System (GPFS) with 10 PB of capacity and an aggregated throughput of 200 GB/s is available. Disk storage subsystems were built by DDN.